I've been noticing some mildly strange behavior with my engine, and now it may be becoming more concrete

[Lex_utor]

On 2/1/2023 at 10:46 PM, eleveneleven said:

Any update on this OP? I'm having a similar issue, engine has started idling a little lower than it used to (around 500rpm now its usually around 700) it's causing the car vibrate when sat still. No fault codes come up when I scan it. 

I've switched from Tesco momentum to Sainsburys super unleaded  as it's a lot closer/convenient so I'm not sure if it's the fuel that's causing the issue or maybe something else, Sticking caliper maybe? 

I scan the car and the only codes I seem to get with Techstream are  C1210 and C1336 codes. Zero point calibration yaw and acceleration. I haven't noticed the problem lately. But the weather is much warmer, if that was helping causing it. But codes related to the engine Techstream finds none.  My calipers are fine but the car is getting new brakes all around this week.

[Steve]

MAF can be dirty so giving wrong reading. get some isopropyl in a can, take out MAF and give the small wire inside a good squirt of this. try not to fiddle with the sensor too much but isopropyl clean will do it wonders. When the wire looks clean, pop back in. This is a cheap way to see if it is MAF.. Clean mine every couple of years.

[AFlex]

The revs going up and down thing does sound very much like a vacuum leak issue. Check all the rubber hoses going into the engine for any holes or gaps. Could also be the brake booster as this is connected to the vacuum lines.

As for the general sloppy performance of the engine - I've had the same issues as you over the last couple of years. I've been gradually replacing wear and tear parts and i'm still not back to peak performance but it has definitely helped:

• spark plugs;
• O2 sensors;
• fuel pressure regulator;
• MAF sensor;
• Oil control valve (OCV) filters;
• EVAP vacuum switch;
• still planning on replacing the in-tank fuel pump and fuel filter as well as all vacuum lines

Hope this is of some use